Add support for undocumented query options for API

api/prometheus/v1/api.go

@@ -1076,9 +1076,19 @@ func (h *httpAPI) LabelValues(ctx context.Context, label string, matches []strin
 	return labelValues, w, err
 }
 
+// StatsValue is a type for `stats` query parameter.
+type StatsValue string
+
+// AllStatsValue is the query parameter value to return all the query statistics.
+const (
+	AllStatsValue StatsValue = "all"
+)
+
 type apiOptions struct {
-	timeout time.Duration
-	limit   uint64
+	timeout       time.Duration
+	lookbackDelta time.Duration
+	stats         StatsValue
+	limit         uint64
 }
 
 type Option func(c *apiOptions)
@@ -1091,6 +1101,24 @@ func WithTimeout(timeout time.Duration) Option {
 	}
 }
 
+// WithLookbackDelta can be used to provide an optional query lookback delta for Query and QueryRange.
+// This URL variable is not documented on Prometheus HTTP API.
+// https://github.com/prometheus/prometheus/blob/e04913aea2792a5c8bc7b3130c389ca1b027dd9b/promql/engine.go#L162-L167
+func WithLookbackDelta(lookbackDelta time.Duration) Option {
+	return func(o *apiOptions) {
+		o.lookbackDelta = lookbackDelta
+	}
+}
+
+// WithStats can be used to provide an optional per step stats for Query and QueryRange.
+// This URL variable is not documented on Prometheus HTTP API.
+// https://github.com/prometheus/prometheus/blob/e04913aea2792a5c8bc7b3130c389ca1b027dd9b/promql/engine.go#L162-L167
+func WithStats(stats StatsValue) Option {
+	return func(o *apiOptions) {
+		o.stats = stats
+	}
+}
+
 // WithLimit provides an optional maximum number of returned entries for APIs that support limit parameter
 // e.g. https://prometheus.io/docs/prometheus/latest/querying/api/#instant-querie:~:text=%3A%20End%20timestamp.-,limit%3D%3Cnumber%3E,-%3A%20Maximum%20number%20of
 func WithLimit(limit uint64) Option {
@@ -1109,6 +1137,14 @@ func addOptionalURLParams(q url.Values, opts []Option) url.Values {
 		q.Set("timeout", opt.timeout.String())
 	}
 
+	if opt.lookbackDelta > 0 {
+		q.Set("lookback_delta", opt.lookbackDelta.String())
+	}
+
+	if opt.stats != "" {
+		q.Set("stats", string(opt.stats))
+	}
+
 	if opt.limit > 0 {
 		q.Set("limit", strconv.FormatUint(opt.limit, 10))
 	}